The present invention relates to a snap-on coupling for connecting a low-pressure fluid pipe to a rigid tubular end fitting, particularly for a fuel supply line or for a brake power line for a vehicle driven by a heat engine. More specifically, the invention relates to such a coupling fitted with a visual indicator for showing correct connection between this end fitting and a sleeve of this coupling into which this pipe is inserted, as well as to a method of visually inspecting this connection.
A snap-on coupling for connecting a fluid pipe to a rigid tubular end fitting is described for example in FR-A1-2 795 156 in the present Applicant's name. That coupling comprises among other things a sleeve mounted in a fixed position on one end of the pipe, and the rigid tubular end fitting, designed to be inserted into the sleeve, has a peripheral projection toward its free end. The coupling is completed by a locking member in the form of a staple or U designed to straddle the sleeve and having two elastically deformable legs capable of engaging in two openings in the sleeve in order to engage with the peripheral projection on the end fitting and thus retain the latter in the sleeve. To facilitate the connection, the locking member is pre-mounted onto the sleeve, and the tubular end fitting is then engaged in the sleeve. This engagement causes the two elastic legs of the locking member to move apart as the peripheral projection of the end fitting passes between them, and the two elastic legs should return to their initial positions after the projection has passed between them in order to retain the end fitting in the sleeve.
The operator making the connection can be confident that the connection is correctly made when the two elastic legs return to their initial positions after the peripheral projection on the end fitting has passed between them, because this produces a characteristic noise which the operator can hear. However, this audible indicator of a correct connection may not be heard by an operator working in a hostile environment with background noise.
Document EP-B1-1 770 321 in the present Applicant's name has a coupling of the type described in that document FR-A1-2 795 156, but which is also fitted with a visual indicator for ensuring correct connection between the end fitting and the coupling without the need for a quiet environment when the coupling is being connected. This indicator, which also consists of a U or staple with one head and two deformable legs, is supported by the sleeve behind the locking member and is designed to engage with the projection on the end fitting so as to move from a depressed position within the sleeve to an extended position out of the sleeve and so provide a visual indication that the end fitting is correctly connected in the sleeve, since the legs of the indicator have inward fixing catches at their free ends which engage with two lower teeth formed on the sleeve when the indicator is in the depressed position and with two intermediate teeth formed on the sleeve when the indicator is in the extended position.